Polyurethane resins have conventionally been used as primers in various industrial fields.
For example, in the field of optical plastic lenses, when a hard-coat layer is formed on a surface of a lens substrate, polyurethane resin is used as a primer for improving adhesion between the surface of the lens substrate and the hard-coat layer.
In recent years, in the field of optical plastic lenses, a method for manufacturing a photochromic lens which colors outdoors to function as sunglasses and discolors indoors to function as a transparent glasses, by forming a photochromic coat layer on a surface of a lens substrate has been known, and it is studied that polyurethane resin is used as a primer in order to improve adhesion between the surface of the lens substrate and the photochromic coat layer.
It has been proposed, for example, to use a moisture-curing polyurethane resin as a primer between the surface of the lens substrate and the photochromic coat layer (see, for example, the following Patent Document 1).    Patent Document 1: International Publication No. WO 2004/078476 A1